Process for curing hydantoin-containing polyacrylates with ionising radiation

ABSTRACT

Process for curing polyacrylates, especially in the form of thin layers or coatings, of the formula   WHEREIN R1 and R2 denote a hydrogen atom or the methyl group and n denotes the number 2 or 3 and A denotes an organic radical which contains at least one grouping   WHEREIN Z represents a divalent radical required to complete a five-membered or six-membered ring, by means of ionising rays, for example electron beams, X-rays or gamma-rays. The resulting coatings show improved weathering resistance, extensibility and gloss retention.

United States Patent 1 1 Garratt et al.

1 1 Nov. 12, 1974 1 PROCESS FOR CURING HYDANTOlN-CONTAINING POLYACRYLATES 'WITH IONISING RADIATION [75] Inventors: Peter Garth Garratt, Wallisellen;

Juergen Habermeier, Pteffingen; Daniel Porret, Binningen; Ernst Leumann; Paul Zuppinger, both of Arlesheim, all of Switzerland [73] Assignee: Ciba-Geigy AG, Basel, Switzerland [22] Filed: Jan. 13, 1972 [21] Appl. N0.: 217,669

[30] Foreign Application Priority Data July 9, 1971 Switzerland 10123/71 [52] U.S. Cl 204/159.22, 1l7/93.31, 117/132 R, 117/132 BE, 117/138.8 R, 204/159.15,

204/159.16, 260/2 EP, 260/41 B, 260/78.4

EP, 260/86.1 E, 260/86.1 N, 260/89.5,

May 260/837 Newey et al. 260/837 Primary ExaminerPaul Lieberman Assistant ExaminerRichard B. Turer Attorney, Agent, or FirmKarl F. Jorda [57] ABSTRACT Process for curing polyacrylates, especially in the form of thin layers or coatings, of the formula wherein R and R denote a hydrogen atom or the methyl group and n denotes the number 2 or 3 and A denotes an organic radical which contains at least one grouping wherein Z represents a divalent radical required to complete a-five-membered or six-membered ring, by means of ionising rays, for example electron beams, X-rays or gamma-rays. I

The resulting coatings show improved weathering resistance, extensibility and gloss retention.

14 Claims, N0 Drawings It is known to bring about the crosslinking of syn- 5 thetic resin polymers by the action of ionising rays, for example X-rays, gamma-rays, beta-particles or beams of greatly accelerated electrons. In most industrial applications of these methods of irradiation, electrons having an energy of between 50 and 4,000 KeV have been used.

It is furthermore known to utilise ionising rays for curing synthetic resin coatings consisting of mixtures of unsaturated polyesters and reactive olefinically unsaturated monomers. These known coatings obtained by radiation curing, whilst generally showing good mechanical properties, also possess some disadvantages for many technical applications, such as, for example, inadequate weathering resistance, inadequate extensibility and impact strength, and low gloss retention.

It has now been found, surprisingly, that coatings with improved weathering resistance, extensibility and gloss retention are obtained if instead of the known synthetic resin coatings of unsaturated polyester resins and reactive monomers coatings of polyacrylates which contain at least one grouping R1 Jr:

wherein R and R independently of one another each represent a hydrogen atom or'the methyl group, n denotes the number 2 or 3 and A denotes an organic radical which contains at leastone grouping in which Z denotes a divalent radical which is required to complete a five-membered or six-membered, unsubstituted or substituted, heterocyclic ring, are used by themselves or, if appropriate, as a mixture with other reactive monomers.

The radical Z in the N-heterocyclic grouping of the formula I preferably only contains carbon and hydrogen atoms or carbon. hydrogen and oxygen atoms. It can, for example, be a radical of the formulae other can each denote a hydrogen atom or, for'example, an alkyl radical, preferablya lower alkyl radical with l 4 C atoms, an alkenyl radical, preferably a lower alkenyl radical with l 4 C atoms, a cycloalkyl radical or an optionally substituted phenyl radical.

,The radical Z can, however, also-consist of a nitrogen-containing radical of the'formula wherein X represents the acryloxyor methylacryloxy- 2-hydroxypropyl or -2-hydroxy-2 methylpropyl radical according to the'formula I.

The polyacrylates of the formula I can be manufactured if n mols'of acrylic acid and/or methacrylic acid are added, in a manner which is in itself known, to 1 mol of a polyglycidyl compound of the general formula wherein R n and A have the same meaning as in the formula I above.

The addition reaction is preferably carried out in the melt; however, it can also be carried out in solution. The addition of the acrylic acid or methacrylic acid is effected at 20l80C, preferably at 60-l40C, without catalysts or in the presenceof basic catalysts. The course of the addition reaction can easily be followed by continuously examining theepoxide content of :the

reaction mixture or by titration of the unreacted acrylic Further suitable catalysts are also low molecular thioethers and sulphonium salts.

As such thioethers or sulphonium salts there may be mentioned: diethyl-sulphide, B-hydroxyethyl-ethylsulphide, B-hydroxypropyl-ethyl-sulphide, w-hydroxytetramethylene-ethyl-sulphide, thiodiglycol, mono-B- cyanoethylthioglycol-ether, dibenzyl-sulphide, benzylethyl-sulphide, benzyl-butyl-sulphide, trimethylsulphonium iodide, tris(B-hydroxy-ethyl)sulphonium chloride, dibenzylmethylsulphonium bromide, 2,3- epoxypropylmethylethylsulphonium iodide, dodecylmethyl-sulphide and dithiane.

The reaction can, however, also be accelerated by adding other suitable alkaline reagents, such as sodium hydroxide, potassium hydroxide, barium hydroxide, calcium hydroxide, sodium carbonate, potassium carbonate and sodium acetate.

The polyglycidyl compounds of the formula II are known compounds and can be manufactured if N- heterocyclic compounds which contain at least one grouping in which Z denotes a divalent radical which is necessary to complete a five-membered or six-membered, unsubstituted or substituted, heterocyclic ring, are reacted in one step or several steps with an epihalogenohydrin or B-methylepihalogenohydrin, such as, for example, epichlorohydrin, B-methylepichlorohydrin or epibromohydrin, with elimination of hydrogen halide, in a manner which is in itself known.

The polyglycidyl compounds of the formula ll used for the manufacture of the polyacrylates of the formula I are above all mononuclear and binuclear N- heterocyclic polyglycidyl compounds. It is, however, also possible to use polyglycidyl compounds wherein the N-heterocyclic ring occurs more than twice in the molecule.

The mononuclear polyglycidyl compounds of the formula [1 correspond to the general formula (III) wherein R represents a hydrogen atom or the methyl group, n denotes the number 2 or 3 and A denotes an organic radical which contains one grouping in which Z denotes a divalent radical which is necessary to complete a five-membered or six-membered, unsubstituted or substituted, heterocyclic ring.

A preferred sub-category of mononuclear N- heterocyclic polyglycidyl compounds of the formula lll corresponds to the formula wherein R and R independently of one another represent a hydrogen atom or the methyl group and Z has the same meaning as in the formula lll. There may be mentioned the N,N'-diglycidyl compound of the formula wherein R andR have the same meaning as in the formula IV and wherein R and R independently of one another each denote a hydrogen atom or a lower alkyl radical with 1 to 4 carbon atoms; examples of this category of compounds are, for example, 1,3- diglycidyluracil, l,3-diglycidyl-6-methyluracil, 1,3- diglycidyl-S-methyluracil and 1,3-di-(B- methylglycidyl)-uracil.

Further, there should be mentioned N,N'-diglycidyl compounds of the formula (VII) wherein R and R have the same meaning as in the formula IV and wherein R and R both d'enote'hydrogen atoms or identical or different alkyl radicals, preferably alkyl radicals with l to 4 carbon atoms, and R and R independently of one another each denote a hydrogen atom or a, preferably lower, alkyl radical with 14 C atoms.

Examples of this category of compounds are, for example, l,3-diglycidyl-5,S-dimethyl-S,o-dihydrouracil, 1,3-diglycidyl-5,5-dimethyl-6-isopropyl-5 ,6- dihydrouracil and l,3 di-(B-methylglycidyl)-5,5- dimethyl-S,6-dihydrouracil. Additionally, attention should be drawn to the N,N-diglycidyl compounds of barbituric acid and of parabanic acid.

A further preferred sub-category of mononuclear N heterocyclic polyglycidyl compounds of the formula III corresponds to the general formula wherein R has the same meaning as in the formula III. Examples of these categories of compounds are triglycidylisocyanurate and tri-(B- methylglycidyl)isocyanurate.

A further preferred sub-category of mononuclear N- heterocyclic polyglycidyl compounds of the formula III corresponds to the general formula T /Rr] 0 o l Ru 11-1 Q 1 ll (IX) wherein R and R independently of one another represent a hydrogen atom or the methyl group and wherein R and R independently of one another each denote a hydrogen atom or an aliphatic, cycloaliphatic, araliphatic or aromatic hydrocarbon radical, such as, in particular, a lower alkyl radical with l to 4 carbon atoms, R R and R each represent an alkyl radical, especially a lower alkyl radical with 1 to 4 carbon atoms, or a hydrogen atom, or R and R together form a divalent aliphatic'or cycloaliphatic hydrocarbon radical, preferably a tetramethylene or pentamethylene radical, and n denotes an integer having a value of l or 2.

As examples of this category of compounds there may be mentioned: l-glycidyloxymethyl-3-glycidyl-5,5- dimethylhydantoin, 1-( l '-glycidyloxyethyl) 3-glycidyl- 5 ,S-dimethylhydantoin, l-glycidyloxymethyl-3- glycidyl-S-isopropylhydantoin, l-glycidyloxymethyl-3- glycidyl-S ,5-tetramethylenehydantoin, lglycidyloxymethyl-3-glycidyl-5-ethyl-5- ethyl]-5,5-dimethylhydantoin,

6 methylhydantoin and l-glycidyloxymethyl-3-glycidyl- 5,S-dimethyl-S,o-dihydrouracil.

A further preferred sub-category of mononuclear N- heterocyclic polyglycidyl compounds of the formula [II corresponds to the general formula glycidyloxy-B-phenylethyl )-5,5-dimethylhydantoin, lglycidyl-3( B-glycidyloxy-fi-phenylethyl )-5-ethyl-5- phenylbarbituric acid, l-glycidyl-3-(B-glycidyloxy-nbutyl)-5,5-dimethylhydantoin and l-glicidyl- S-(B- glycidyloxycyclohexyl )-5 ,S-dimethylhydantoin.

The binuclear polyglycidyl compounds according to the formula ll used for the manufacture of the polyacrylates of the formula] correspond to the general formula wherein R represents a hydrogen atom or the methyl group and A" denotes an organic radicalof the formula in which Z and Z independently of one another each denote a divalent radical which is necessary to complete a five-membered or six-membered, unsubstitutedor substituted heterocyclic ring, and B represents a divalent aliphatic, cycloaliphatic or araliphatic radical, and in particular preferably an alkylene radical, or an alkylene radical which is interrupted by oxygen atoms or ester groups.

A preferred sub-category of binuclear N,N'-

I diglycidyl compounds of the formula Xl corresponds to the general formula wherein R and R independently of one another represent a hydrogen atom or the methyl group and R R gory of compounds are, for example 3,3-diglycidyl- 1,1 -methylene-bis-( 5,6-dihydrouracil), 3,3 diglycidyl-1,1-methylene-bis-(6-methyl-5,6- dihydrouracil 3,3'-diglycidyl-l,l methylene-bis- (5,S-dimethyl-S,6-dihydrouracil) and 3,3-di-(,8- methylglycidyl)-1,1'-methylene-bis-(5,6- dihydrouracil).

A further preferred sub-category of binuclear N,N'- diglycidyl compounds of the formula Xl corresponds to R and R each de rttl'te ahydrogen atom or a lower the general formula alkyl radical with l to 4 carbon atoms, or wherein R and R or R and R together form a tetramethylene or pentamethylene radical; examples of this category of compounds are, for example, bis-(3-glycidyl-5,5- dimethylhydantoinyl-l )-methane, bis-( 3-glycidyl-5- methyl-5-ethylhydantoinyl-l )-methane and bis-( 3- glycidyl-5-propylhydantoinyl-1 )-methane.

A further preferred sub-category of binuclear N,N'- diglycidyl compounds of the formula Xl corresponds to the general formula (XIII) wherein R and R have the same meaning as in the formula Xll, B represents an aliphatic, cycloaliphatic or araliphatic radical and R R R and R each denote a hydrogen atom or a lower alkyl radical with l to 4 (XIV) wherein R and R have the same meaning as in the formula Xll and R R R and R independently of one another each denote a hydrogen atom or a lower alkyl radical with l to 4 carbon atoms; examples of this cate- 2 If R2 wherein R and R have the same meaning as in the formula XII, Y, and Y each represent a hydrogen atom, a methyl group, an ethyl group or a phenyl group, 2, and Z independently of one another each denote a nitrogen-free, divalent radical which is necessary to complete a five-membered or six-membered, unsubstituted or substituted heterocyclic-ring, D represents the hydrocarbon radical of a dicarboxylic acid obtained by removing the carboxyl groups and n denotes the number 1 or 2.

Examples of this category of compounds are, for example, sebacic acid bis-(N-glycidyl-5.5- dimethylhydantoinyl-3-2-hydroxy-n-propyl ester). sebacic acid bis-(N-glycidyl-S,5dimethylhydantoinyl-3- 2-hydroxy-n-butyl ester), glutaric acid bis-(N-glycidyl- 5,5-dimethylhydantoinyl-3-2'-hydroxy-n-propyl ester) and succinic acid bis-(N-glycidyl-5,5- dimethylhydantoinyl-3-2'-hydroxyethyl ester).

A further possible category of suitable polyglycidyl compounds are those which contain more than two of the N-heterocyclic rings in the molecule. These compounds can be manufactured if dicarboxylic acids are reacted with diglycidyl compounds in the appropriate molar ratio.

Possible monomers which can be added to the polyacrylates of the formula (I) are above all compounds of the acrylic acid series, such as esters of acrylic acid or methacrylic acid and alcohols or phenols, for example methyl acrylate, ethyl acrylate, butyl acrylate, dodecyl acrylate and methyl methacrylate; acrylonitrile, methacylonitrile and ethylene glycol dimethacrylate. Furthermore, it is also possible to use other reactive olefinically unsaturated monomers, such as, for example, styrene, divinylbenzene, vinyl esters, such as vinyl acetate, allyl compounds, such as diallyl phthalate and others.

The polyacrylates which are particularly suitable for the manufacture of coatings can additionally contain plasticisers, fillers and, preferably, pigments, for example titanium dioxide. 5,5-dimethylhydantoin and lglicidyl- The polyacrylate mixtures show good adhesion to the surface of the base material so that coatings on metals, wood, plastics, glass, paper, leather and the like can be produced without difficulties.

The curing of the polyacrylates can be effected with any ionising radiation, preferably with a high energy electromagnetic radiation, such as, for example X-rays or gamma-radiation, and with accelerated electrons. in the latter case, an average electron energy of 50 keV to 4,000 keV is used. If the curing of thin layers, such as, 'for example coatings, is involved, an average elecglycidyloxy-n-propyl)-5,5-dimethylhydantoin (0.591 tron energy of 50 to 600 keV and a curing dose of 0.5 mol) are stirred at 100C. 0.3 g of anhydrous sodium to 5.0 Megarad, preferably of 1.0 to 3.0 Megarad is acetate and 0.1773 g of hydroquinone are added and used. 102.2 g of distilled methacrylic acid (1.182 mols) are The polyacrylates can advantageously be additionally 5 added dropwise thereto over the course of 30 minutes. subjected to a heat treatment before, during or after When half the amount of acid has been added dropcuring, which in some cases facilitates the crosslinking. wise, 0.0591 g of hydroquinone are added. After the The curing is appropriately carried out in the absence dropwise addition, a last hydroquinone addition of of oxygen. To achieve this, a protective gas atmo- 0.0591 g is stirred into the reaction mixture and the sphere, for example nitrogen, is used. to temperature is raised to 125C.

In some cases it is advantageous to add small 75 minutes after completion Of the addition of the amounts of a polymerisation catalyst which forms free h cry d, the epoxide Content has dropped to I radicals, such as for example, peroxides 3Z0 m 0.768 equivalents/kg. 5 hOUI'S after the dlOpWlSC fiddlpounds and persulphates, to the polyacrylates. tion it has pp to (1147 q alent/kg.

In the examples which follow unless therwise 15 Acomparison experiment WllhOLlt the addition Dist)- 1 t d, parts denote parts b i h d percentages dium acetate shows an epoxide content of 1.43 equivadenote percentages b i h lents/kg (as compared to 0.768) 75 minutes after com- Manufacture f h p]yacry]ates pletion of the dropwise addition of the methacrylic acid p l l t A to the reaction mixture; hours after the dropwise ad- 1,017 g (corresponding to 3 mols) of a technically 20 dition, 0.39 epoxide equivalent/kg are still present (as manufactured 1 glycidy] 3 (B-glycidyloxy-n-propyl)- compared 0.147). The content Of polymerisable 5,5-dimethylhydantoin (epoxide content: 5.9 equivadouble bonds is q i len s/kg. l t /k are warmed to 1 10C Both products essentially correspond to the following addition of 432.4 g of acrylic acid is started immedi- Polyacrylate C ately. After 10 minutes, one-third of the acrylic acid 3,964 g of sebacic acid bis-(N-glycidyl-5-.5- has been added and the reaction becomes so exotherdimethylhydantoinyl-3-(2'-hydroxy-n-propyl) ester) mic that after removal of the heating bath the temperahaving an epoxide content of 3.045 equivalents/kg ture rises to 125C. 6.035 mols) are heated to 1002 C in a dry glass appara- After minutes, a further 2.9 g of hydroquinone are tus of 6 litres capacity, equipped with astirrer, theradded. After a total of 35 minutes the entire amount of mometer, reflux condenser and dropping funnel. 9.6 g acrylic acid has been added and after the exothermic of hydroquinone are added whilst stirring and the dropeffect has subsided the reaction mixture is stirred at wise addition of 869.8 g of freshly distilled acrylic acid 120-130C. 20 minutes after completion of the dropis started immediately. The time for the dropwise addiwise addition the epoxide content of the reaction miX- tion is minutes. The reaction becomes exothermic. ture is 1.36 equivalents/kg. minutes later, the con- After removal of the heating bath, the reaction mixture tent of epoxide groups has dropped to 0.3 equivareaches atemperature of C. The mixture is stirred lent/kg. The clear liquid is introduced into a dark botfor afurther 8 hours at 125C and the clear, pale yeltle. After cooling, the adduct, which is produced quanlowish liquid is poured into a dark glass bottle.

titatively, is aviscous liquid; the epoxide content is 0.23 An adduct wherein the residual epoxide content is equivalent/kg, corresponding to approx. 95% addition. only about 0.09 equivalent/kg is obtained in quantita- The content of polymerisable double bonds in the tive yield. The average molecular weight determined by product is 4.2 equivalents/kg and the product princivapour pressure osmometry is 697 (theory 698.9).

pally corresponds to the following structure: 55 The content of polymerisable double bonds is 2.5

H30 CH3 0 H o p -(l: on. 0H 0 H,o=b-l J-,0oH,( 3H-oH,N N cH,- JH-o-GH,-cHCH,-O-d-CH=GH,

Polyacrylate B equivalents/kg. Accordingly, the adduct essentially 206 goftechnically manufactured l-glycidyl-3-(B- corresponds to the structure:

equivalent) ofa technical l-glycidyl-3-(2'-glycidyloxyn-propyl)-5,5-dimethylhydantoin (epoxide content 5.58 equivalents/kg) are reacted with 60.6 g (0.6 equivalent of sebacic acid with the addition of 0.8 g of triphenylphosphine, at l 10l25 internal temperature,

raised to l-l40C and the mixture is left to react until practically all the epoxide groups have been ester ified, which is the case after 4-5 hours. A yellow resin which is highly viscous in the cold is obtained in quantitative yield; it has an epoxide content of 0.06 equivalent/kg and a content of polymerisable double bonds of 1.2 equivalents/kg, and is principally to be ascribed the until an acid number of 05 is reached; this is the case 20 following str t re;

CH: O

to i

after approx. 1 hour. The exothermic reaction which occurs in the interim is kept at the indicated tempera- C HO-JJH ll 0 CH3 Polyacrylate E If instead of the ratio of 0.9 equivalent of the epoxide ture by occasional cooling. As a result of the differing compound used for the manufacture of polyacrylate D,

reactivity of the two esterifiable epoxide groups, an intermediate product of principally the following structure:

and having an epoxide content of 1.28 equivalents/kg (calculated: 1.35) is obtained.

b. This intermediate product is now stabilised with 0.8 g of hydroquinone and 2l.6 g of acrylic acid (0.3

0.6 equivalent of sebacic acid and 0.3 equivalent of acrylic acid, a ratio of 0.8 equivalent of the same epoxide compound, 0.4 equivalent of sebacic acid and 0.4

equivalent of acrylic acid is employed and in other respects the reaction is carried out in the same manner as described for the manufacture of polyacrylatc C. a yellow resin which is highly viscous when cold is obtained in quantitative yield; it has a content of polymerisable double bonds of 1.9 equivalents/kg and is to be ascribed principally the following structure:

CH3 CH3 0 o H OH 0 be ll '1 do in; H

H2 r H2 Example 1 Example 2.

90 mp thick films of polyacrylates A to E and mix- 60 my. thick films of a solution manufactured from tures of these polyacrylates and polymerisable mono- 70 parts of polyacrylate A and 30 parts of butyl acrymers according to Table l and Table 2 were applied to late were applied to steel sheets pretreated with zinc electrolytically pretreated iron sheet (sheet thickness phosphate (Granodine 6005 sendzimir galvanised 0.3 mm). After about 1 minute, these films were exsteel, sheet thickness 0.75 mm). These steel sheets posed to acc e electrons of average gy 400 were irradiated as described in Example 1. Thereafter kev y Passing the Sheets longitudinally gh an the films were immediately examined for their surface electron beam (radiation intensity 4 Megarad/second). ta kin nd th ir surface hardness according to the 1 after, the films were immediately examined for surface tackiness and their surface hardness was tested with a I with toluene. Tables 1 and 2 below show the results ob- The irradiations were carried out in a nitrogen atmomethod described in Example 1 [t was f d that the Sphere (maxlmum Oxygen concenlratlgn There films can be fully cured with a radiation dose of 2.0

Megarad.

After some days, the films were examined further. The dry layer thickness was determined according to VDI 2451 (non-destructive test). The film thickness was 35 mg. The scratch hardness of the lacquer was determined with a hardness test rod (according to Erichsen; type 318). The films reached a value of 175 p (on the Erichsen scale). The adhesion was determined by the cross-cut method according to DIN 53,151 (with subsequent pulling-off with Tesafiltn). A cross-cut of 0 was found. The behaviour of the lacquer on bending the material was tested by the mandrel bending test according to DIN 53,152. The coating was undamaged on Table 1 35 bending around the 2 mm mandrel. The deformability of the coated material was determined by deep-drawing Curing dose and percentage of insoluble matter of cured polyacrylates according to DIN 51156 deepdraw of 8 steel blade, using a simple test method. The resistance of the synthetic resin films to chemical solvents was tested by applying a drop of toluene (and acetone) and I the proportion of insoluble matter was determined in a Soxhlet extraction apparatus by 24 hours extraction tained. The curing dose is the .minimum radiation dose which is required to produce a non-tacky. film of good surface hardness.

It was found that at the indicatedcuring dose a high degree of crosslinkingof the films is obtainable.

of N-heterocyclic compounds I the coating developed cracks; The pendulum hardness Pol acr late C=C double bond Curin dose Insoluble of films was deIQrmi-ned according) DIN 53,157 y y content/kg (Meg arad) matter in 7: 4O (Konlgy The films a ll c a Pendul ha of 140 seconds. A 4.2 0.75 100 3 B 4,05 15 00 Mixtures of parts of polyacrylate C, 20 parts of C 25} 100 butyl methacrylate and 30 parts of titanium dioxide.

' 5 (RCR-3) was applied to hardboard sheets obtainable D 1.2 2.5 95 under the registered trademark Pavatex from Papier- E 9 t m 82 fabrik Cham AG (film thickness u) and were irradiated in the same manner as described in Example 1.

' Table 2 Curing dose and percentage of insoluble matter of cured mixtures of polyacrylates of N-heterocyclic compounds and polymerisation monomers Polyacrylate Monomer I Weight ratio of Curing dose Insoluble matter in polyacrylate:

monomer (Megarad) Butyl acrylate 70 30 I L5 96 A Methyl methacrylate 70 30 L5 85 Styrene 70 30 7.0 I00 Butyl acrylate 70 30 [.5 98 B Methyl methacrylate 70 30 3.0 I00 Styrene 70 30 5.0 85

Butyl acrylate 1 80 20 2.0 92 C Methyl methacrylate 80 z 20 2.5 95 Styrene 80 20 4.0 99

, Butyl acrylate 80 20 3.5 92 D Methyl mcthucrylute 80 20 3.5 )2 Styrene 80 20 6.0

Butyl acrylate 80 20 4.0 82 E Methyl methacrylate 80 20 4.0 84 4.0 74

Styrene 80 20 The requisite curing dose was 4.5 Megarad (the dry layer thickness was approx. 55 ,u).

The film properties were further examined after 24 V Table 3 Percentage of insoluble matter of mixtures of polyacrylate C and polymerisable monomers cured at various curing doses Polyacrylate Monomer Weight ratio Insoluble matter of polyacrylate:monomer 0.25 0.5 0.75 1.0 1.25

Mrad Mrad Mrad Mrad Mrad C I 0 94 99 99 100 100 C Styrene 70 30 Liquid 97 98 99 100 C Butyl acrylate 70 30 60 99 99 99 99 C Methyl methacrylate 70 30 Liquid 87 97 97 100 hours. The surface hardness was determined according We claim:

to SNV 37,113 (pencil hardness) and DIN 53,153 (Buchholz). The films attained a pencil hardness of 2-3 H and a Buchholz indentation resistance of 91. The scratch hardness (according to Taber) was 400 g. A cross-cut of 1 (according to DIN 53.151, with subsequent pulling off with Tesafilm) was measured. The abrasion resistance was tested with a Taber test apparatus (clamping device, CS-l7 grindstone, 2 X 500 g load). An abrasion of mg/SOO revolutions was found. The coatings have good resistance to chemicals; none of the customary household liquids such as sodium carbonate solution or soap solution leads to damage. Good resistance to keys was found.

Example 4 60 p. thick films of a mixture based on polyacrylate B in butyl acrylate (70 30) were applied to ABS (acrylo-nitrile-butadiene-styrene) plastic sheets and irradiated in the same manner as described in Example 1. The requisite curing dose was 2.5 Megarad.

The subsequent test shows that the films reached a pencil hardness of F-H (according to SNV 37,1 13) and a Buchholz indentation resistance (DIN 53,153) of 100. The scratch hardness (according to Erichsen hardness test rod type 318) was 175 p. A cross-cut of 0 (according to DIN 53,151, with subsequent pullingoff with Tesafilm) was measured. The films furthermore attained a pendulum hardness (according to DIN 53.157) of 150 seconds.

The lacquer coatings are distinguished by improved abrasion resistance and scratch resistance as compared to the untreated ABS plastic sheets. The untreated sheets have a scratch hardness of 50 p (measured according to the Erichsen scale). The adhesion of the films was excellent.

Example 5 Polyacrylate C and mixtures of polyacrylate C and polymerisable monomers (according to Table 3) are introduced into tubes of 1.25 cm diameter up to a height of about 2.5 cm and exposed to the gamma radiation of a C0 source of rays. These experiments were carried out at approx 30C and in the presence of oxygen. After the irradiation, the degree of crosslinking was determined by extraction with toluene in accordance with the procedure described in Example 1. All experiments were carried out at a radiation intensity of 0.9 Megarad/hour. Table 3 shows the percentage of insoluble matter which was obtained at irradiation doses of 0.25, 0.5, 0.75. 1.0 and 1.25 Megarads from polyacrylate C alone or mixed with polymerisable monomers. The table which follows shows that the polyacryl- 1. Process for curing polyacrylates by means of ionizing rays selected from accelerated electron rays in the dosage of from 0.5 to 7 Megarads and gamma radiation in the dosage of from 0,25 to 1.25 Megarads, said dosages producing nontacky films characterized in that compounds of the formula I in which 2 aenot'a a aivarea'imamms *reqa'raa' to complete a five-membered or six-membered, unsub-, stituted or substituted, heterocyclic ring, are irradiated.

2. Process according to claim 1, characterized in that polyacrylates of formula I mixed with olefinically unsaturated monomers in the ratio of 66 to to 34 to 20 parts by weight, respectively, are irradiated.

3. Process according to claim 1, characterised in that the curing of the polyacrylates is effected with an ionising radiation by means of electrons of average energy at least 50 keV and at most 4 MeV. I

4. Process according to claim 1. characterised in that the curing of the polyacrylates is effected with an ionising radiation by means of electrons of average energy 50 to 600 KeV.

5. Process according to claim 1, characterised in that the curing of the polyacrylates is effected with an ionising radiation in the form of gammarays.

6. Process according to claim 1, characterised in that the polyacrylates are additionally subjected to a heat treatment before, during or after the action of an ionising radiation.

7. Process according to claim 1, characterised in that the action of an ionising radiation on the polyacrylates is allowed to take place in an atmosphere of low oxygen content.

" wherein R and R independently of one another eac 17 p 18 8. Process according to claim 1, characterised in that H3O CH; polyacrylates of the formula I are used, in which the radical A contains one hydantomylene group. 1 l

9. Process according to claim 1, characterised in that polyacrylates of the formula I are used in which the H radical A den ss a. radi of the formula R3 11. Process according to claim 1, characterised in i 0:0 that polyacrylates of the formula I are used in which the radical A contains at least two hydantoinylene groups. N NCH-OHO 12. Process according to c|a|m 11, characterised in fi that polyacrylates of the formula I are used in which the 0 radical A denotes a radical of the formulae H3C\ /CH3 H3C\ /CH3 o-o=0 CH; CH1 0=t|1t|3 N NCH;C-OC-(CH;)r-C-OCHCH;N N-

o H o [I ll 0 0 (F113 CHa (EH3 O=CCCH3 CH3-C(F=O (?H3 0-o H-CH -N NCH;CH-CHz- O 0 C-(CHflg-C 0 o-oHi-o HCH;N\ /NCH1C H-O o H OH i O CH: CH:

denote a hydrogen atom or a lower alkyl group, Y represents a hydrogen atom orthe methyl group and Y represents a hydrogen atom or the methyl, ethyl or phenyl group, or wherein Y and Y together denote the r methxlene rlqrarnqthylsas ra ca -W a 10. Process according to claim 9, characterised in that polyacrylates of the formula I are used to which he r dical .Arlerio e a radical Of the for u a OH CH C=O CH:

1 ICH,( 3HOCHz i -4311 CH3 0=C-( JCH3 0H NcH,oH0H,-0 0 C(CH2)8C 0 0oH, 1 g/ 13. Process according to claim 2, characterised in that the curable polyacrylate mixture contains methyl acrylate, butyl acrylate, methyl methacrylate, acrylonitrile, styrene, ethylene glycol dimethacrylate, divinylbenzene, vinyl acetate or diallyl-o-phthalate as the monomer 14. Process according to claim 1, characterised in that the curable synthetic resin mixture additionally Econtains fillers, pigments and/or plasticisers. 

1. PROCESS FOR CURING POLYACRYLATES BY MEANS OF IONIZING RAYS SELECTED FROM ACCELERATED ELECTRON RAYS IN THE DOSAGE OF FROM 0.5 TO 7 MEGARADS AND GAMMA RADIATION IN THE DOSAGE OF FROM 0.25 TO 1.25 MEGARADS, SAID DOSAGES PRODUCING NONTACKY FILMS CHARACTERIZED IN THAT COMPOUNDS OF THE FORMULA I
 2. Process according to claim 1, characterized in that polyacrylates of formula I mixed with olefinically unsaturated monomers in the ratio of 66 to 80 to 34 to 20 parts by weight, respectively, are irradiated.
 3. Process according to claim 1, characterised in that the curing of the polyacrylates is effected with an ionising radiation by means of electrons of average energy at least 50 keV and at most 4 MeV.
 4. Process according to claim 1, characterised in that the curing of the polyacrylates is effected with an ionising radiation by means of electrons of average energy 50 to 600 KeV.
 5. Process according to claim 1, characterised in that the curing of the polyacrylates is effected with an ionising radiation in the form of gammarays.
 6. Process according to claim 1, characterised in that the polyacrylates are additionally subjected to a heat treatment before, during or after the action of an ionising radiation.
 7. Process according to claim 1, characterised in that the action of an ionising radiation on the polyacrylates is allowed to take place in an atmosphere of low oxygen content.
 8. Process according to claim 1, characterised in that polyacrylates of the formula I are used, in which the radical A contains one hydantoinylene group.
 9. Process according to claim 1, characterised in that polyacrylates of the formula I are used in which the radical A denotes a radical of the formula
 10. Process according to claim 9, characterised in that polyacrylates of the formula I are used to which the radical A denotes a radical of the formula
 11. Process according to claim 1, characterised in that polyacrylates of the formula I are used in Which the radical A contains at least two hydantoinylene groups.
 12. Process according to claim 11, characterised in that polyacrylates of the formula I are used in which the radical A denotes a radical of the formulae
 13. Process according to claim 2, characterised in that the curable polyacrylate mixture contains methyl acrylate, butyl acrylate, methyl methacrylate, acrylonitrile, styrene, ethylene glycol dimethacrylate, divinylbenzene, vinyl acetate or diallyl-o-phthalate as the monomer.
 14. Process according to claim 1, characterised in that the curable synthetic resin mixture additionally contains fillers, pigments and/or plasticisers. 